There are several concerns surrounding IUD insertion at the time of an initial visit to a health care provider. One problem with insertion outside the first week of the menstrual cycle may be "window" pregnancies those that occur during the first cycle with the IUD in place. For OCPs initiated with the Quick Start protocol, the pregnancy rate is approximately 2% (Westhoff 2007). No data exist for IUDs that insertion during any other part of the cycle differs with regard to number of window pregnancies. Another theoretical drawback to immediate IUD initiation is insertion in the setting of an undiagnosed STI. While the risk of developing pelvic inflammatory disease (PID) is highest in the 20 days postinsertion, the incidence of pelvic inflammatory disease among IUD users is rare and estimated at between 1:100 to 1:1,000 woman-years (Martinez 2009). Evidence does not support routine screening for sexually transmitted infections prior to IUD insertion for women at low risk for STIs, and testing should be done based on local prevalence data (Walsh 1998; Skjeldestad 1996). For women younger than 26 or with multiple sex partners, screening can be done on the same day of insertion. However, variation in individual provider practice patterns can be an additional barrier that delays IUD insertion and puts women at risk for interval pregnancies while awaiting IUD insertion.